my broker says friday. But what is the latest time for CBOE to accept the exercise? If it is sometime on Saturday, then any important news happening after Friday's market close will put our retail clients in disadvantage.

what is the exact cut-off time for option exercise? Is there an offical time or made by the broker?

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Saturday is expiration day.

However, the cutoff time is always Friday - after the market closes. But each broker establishes its own cutoff time. The OCC may accept exercise notices FROM THE BROKER until a specific time, but you don't care about that time. You need to know you brokers's limit. So ask.

Remember these days options are automatically exercised if they finish ITM by one penny or more. Y